This present invention relates generally to a tamper-indicating closure and a method for manufacturing that closure. More particularly, the present invention relates to a tamper-indicating closure having a plurality of locking projections that are molded to extend from the tamper-indicating ring radially inwardly and upwardly at a predetermined radius of curvature. After molding, during removal of a male core portion from the molded closure, the projections temporarily bend downwardly from their predetermined radius of curvature. A strain relief recess, located radially outwardly from the locking projections, substantially reduces the extent of plastic deformation of the projections during removal of the male core portion. Thus, following removal of the male core portion, the projections elastically return to substantially their predetermined radius of curvature. Because the projections are able to elastically return, secondary heating and physical manipulation steps are eliminated.
It is important to provide tamper-indicating features on bottles and other containers. Increasingly, consumers have come to expect containers of all types that contain substances for human consumption to be equipped with tamper-indicating features. Although the use of such closures is widespread, the expense involved in producing such tamper-indicating closures has limited their use. If tamper-indicating closures could be manufactured less expensively than under current methods, they would be even more widely used.
One approach to providing a tamper-indicating closure is to provide an upper cap portion and a lower tamper-indicating ring which is detachably connected to the cap portion by a failure line. Under this approach, typically, constructions employ a plurality of resilient flexible projections or fingers which extend upwardly and radially inwardly from the lower tamper-indicating ring. Once the closure is applied to the container neck, these upwardly and inwardly directed projections move to engage an annular locking ring portion located on the container neck. When the closure is unscrewed from the neck of the container, the tamper-indicating ring becomes detached from the cap portion and remains on the container neck. Thus, when the cap portion is replaced on the container neck, an identifiable gap forms between the cap portion and the tamper-indicating ring which serves as a visual indication that the container has been previously opened.
Previous molding processes that have been used to manufacture thermoplastic tamper-indicating closures did not mold the projections in their final upward and radially inward positions. This is due to the fact that once the tamper-indicating closure is formed between female and male mold portions, it was necessary to remove the male mold portion from within the formed closure. If the projections were molded in their final upward and radially inward positions beneath the male mold portion, removal of the male mold portion from within the closure would cause these projections to bend severely and break off from the tamper-indicating ring. Instead, under these previous molding processes, closures were molded having projections that point straight down in an unbent fashion. In this manner, bending and breaking off of the projections during removal of the male mold portion was avoided. However, after removal of the male mold portion, post-forming operations became necessary to bend the projections upwardly to their final upward and radially inward positions. Due to the memory nature of thermoplastic materials, it was then necessary for the projections to be heated to re-set them from their straight down unbent configuration to their final upward and radially inward orientation. These post-forming steps increase manufacturing costs and cycle time. Additionally, these post-forming steps introduce unwanted variability into the manufacturing process. As a result, tamper-indicating closures manufactured utilizing these post-forming steps are costly and yield a product that is not sufficiently uniform in configuration.
Thakor et al. (U.S. Pat. No. 5,846,471) discloses a method and apparatus for manufacturing a tamper-indicating closure whereby the tamper-indicating projections are molded in their final position to extend radially inward and upward. Upon removal of the male mold portion from the closure, the plurality of projections must bend downwardly to a degree that is substantially parallel to the longitudinal axis of the apparatus. Such a degree of downward bending subjects the projections to significant deformation which prevents these projections from returning anywhere near their final orientation after removal of the male mold portion. Rather, under Thakor et al., after removal of the male mold portion, the projections bend inwardly to a position that is somewhere intermediate between straight down, unbent and their final molded orientation. Thus, after removal of the male mold portion, in order to return the projections to their final molded orientation, i.e., upward and radially inward, it is necessary to perform a secondary operation whereby the male mold portion is utilized to physically urge the downwardly bent projections to their originally molded position. Apparently, because the projections were molded in their final form rather than pointing straight down, no heating step is necessary to set the projections in their final orientation. Although Thakor et al., appears to be an improvement over the prior art molding processes discussed above because it apparently has eliminated a heating step, there still remains a post forming step which is required to urge the deformed projections to their originally molded orientation
It is an object of the present invention to overcome these drawbacks and to provide a method for producing a tamper-indicating closure having resilient projections which elastically return substantially to their final position after removal of the male mold portion. The inventive closure requires no post forming operations such as physical manipulation or heating as discussed above.
Accordingly, it is a general object of this invention to provide a unitary tamper-indicating closure with resilient locking projections that overcomes the disadvantages of prior art.
It is a more specific object of this invention to provide a unitary tamper-indicating closure with resilient locking projections that has a high durability and long life span.
It is a more specific object of this invention to provide a unitary tamper-indicating closure with resilient locking projections that eliminates secondary heating and physical manipulation steps during the manufacturing process resulting in less manufacturing costs.
It is also a specific object of this invention to provide a unitary tamper-indicating closure with resilient locking projections which is simple in construction.
It is also a specific object of this invention to provide a unitary tamper-indicating closure with resilient locking projections which is reliable in operation and easy to use.
These and other objects of this invention are achieved by providing a method for manufacturing a tamper-indicating closure having a plurality of resilient flexible projections bent upwardly and radially inwardly at a predetermined radius of curvature. The first step in the method includes providing a mold assembly comprising a female mold portion for forming the outer surface of the closure and a male mold portion for forming the closure""s inner surface and its plurality of projections. The male and female mold portions are arranged for relative movement toward and away from each other between a mold open position and a mold closed position. When in the mold closed position, the male and female mold portions define a mold cavity in which the tamper-indicating closure is molded. The next steps in the method are to move the male and female mold portions into the mold closed position; to provide a mold material into the mold cavity; and, to maintain the mold portions in the mold closed position for a predetermined time period until the tamper-indicating closure is formed with its projections disposed at their predetermined radius of curvature. Next, the male mold portion is removed from the molded closure, whereby the projections temporarily bend from their predetermined radius of curvature to a second position. The closure includes a plurality of strain relief recesses corresponding to the number of projections, each strain relief recess being located radially outwardly from each projection. Each recess, in combination with the radius of curvature, acting to limit the extent of permanent deformation of the corresponding projection during removal of the male mold portion so the projection can elastically return to substantially its xe2x80x9cas moldedxe2x80x9d configuration.
In a variation of the disclosed embodiment, the male mold portion comprises an inner core member, a skirt member and an outer core member. The resilient flexible projections of the closure are formed between a molding surface disposed on the outer core member and a molding surface disposed on the skirt member. Prior to the step of removing the male mold portion from the molded tamper-indicating closure, the method further includes the step of separating the molding surface disposed on the outer core member from the bottom surface of the closure projections.
In another variation of the disclosed embodiment, following the step of separating the molding surface of the outer core member from the bottom surface of the closure projections, the method further includes the step of separating the female mold portion from the molded tamper-indicating closure.
In another variation of the disclosed embodiment, the inner surface of the closure includes an integrally molded internal screw thread arranged for engagement with an external screw thread disposed on the inner core member. The mold assembly includes a stripper ring arranged to be positioned against the closure to resist rotational movement of the closure during removal of the male mold portion. Under this variation, the step of removing the male mold portion from the closure includes the sub-step of rotating the inner core member while utilizing the stripper ring to maintain the closure non-rotational which causes the inner core member to unscrew from the closure.
In another variation of the disclosed embodiment, the mold assembly additionally comprises a knock-out bar arranged for movement between a retracted position to an extended position. Following the step of removing the male mold portion from the molded tamper-indicating closure, the method comprises the additional step of moving the knock-out bar from the retracted position to the extended position to eject the closure from the stripper ring.